1. Field of the Invention
The present invention relates to an egg inspecting apparatus, for detecting blood in shell eggs, used at an inspecting station of an egg grading and packaging system for automatically and non-destructively inspecting eggs to find blood in shell eggs known to the trade as “bloods” in which blood is spotted on the yolk surface of an egg or distributed on the white of an egg. The present invention also relates to a method of inspecting the eggs and an egg grading and packaging system utilizing the egg inspecting apparatus to perform the egg inspecting method.
2. Description of the Prior Art
According to USDA Agricultural Statistics in 1991, egg production in 1990 was 553 billions in the world, including 159 billions in China, 82 billions in USSR and 68 billions in the United States. In Japan, about 40 billion hen's eggs (about 2.5 million tons) are produced each year and about 70% (about 28 billion eggs) of them is packaged with one pack containing 10 eggs on average. To provide egg packs each containing 10 eggs, an egg grading and packaging system having a capability of handling some ten thousands of eggs to a fraction of one million eggs per hour is largely employed. In this egg grading and packaging process, only normal eggs are necessarily packaged while defective eggs such as bloody eggs having their yolk surface spotted with blood or having blood distributed on their white, dirty eggs having fowl droppings on an outer surface thereof and cracked eggs have to be rejected unmistakenly.
Hitherto, an egg inspecting method to determine if an egg is a bloody egg is largely practiced, in which eggs are generally inspected by observing the coloring of each of the eggs with naked eyes from above while the eggs are illuminated by a beam of light projected from below onto each of the eggs within a dark room. However, this known method requires an inspector to be well skilled and, accordingly, depending on the degree of skill and fatigue suffered by the inspector, the accuracy of inspecting results and the reproducibility tend to fluctuate. Also, with the known egg inspecting method, there is an additional problem in that so far as colored eggs having a rose-pink or brown shell are concerned, such eggs cannot help but being shipped without being sufficiently inspected because of a partial overlapping between absorption wavelength regions exhibited respectively by hemoglobin (a blood component) and protoporphyrin which is a pigment of an egg shell. In view of this, various optical egg inspecting methods including an optical type have been suggested in and practiced by, for example, U.S. Pat. No. 2,823,800 and the Japanese Patent Publication No. 51-48,995.
On the other hand, in the conventional egg grading and packaging system, the eggs are transported in a plurality of rows (six rows in most cases) by means of associated transport rollers past stations such as cleansing, drying, aligning, inspecting and weighing stations and are then transferred onto a single row of associated transport rollers that transport the eggs to a packaging station where after the total weight has been adjusted uniformly, the eggs can be packaged. However, when the eggs having been transported by multi-row transport rollers are transferred onto single row transport rollers, the transport speed increases in inverse proportion to a factor of reduction in number of the rows (for example, six folds in the case where the eggs having been transported by six-row transport rollers are transferred onto single row transport rollers) and, accordingly, where it is desired to increase the handling efficiency by utilization of a system in which the transport speed with the multi-row transport rollers is increased to the permissible uppermost limit at which breakage of some of the eggs being transported will not occur, it is dangerous for the eggs to be transferred onto the single row transport rollers.
While requirements to reduce the egg handling time, that is, to increase the egg transport speed are currently increasing, a technique has been developed to efficiently package eggs while the latter are transported by a multi-row transport system without the eggs being transferred onto the single row transport rollers from the multi-row transport rollers, such as disclosed in, for example, the Japanese Laid-open Patent Publication No. 2002-153,160. Accordingly, it is desirable that the egg inspection also be performed efficiently and highly accurately while the eggs are transported by the multi-row transport system. By way of example, an egg inspecting method such as suggested in the Japanese Laid-open Patent Publication No. 6-43,093 appears to be effective in performing the egg inspection at a site preceding a packaging process in a single row transport system. However, in terms of performance and cost, an effective egg inspecting method has not yet been developed which suits to the high speed multi-row transport system.
As discussed hereinabove, the optical egg inspecting method has made it possible for the bloody eggs to be inspected with relatively high accuracy so long as the egg shell is white-colored. However, when it comes to the colored eggs such as having rose-pink or brown egg shells, the accuracy of inspection is considerably low and the practicability is also low because the absorption wavelength exhibited by hemoglobins contained in the bloody eggs and that exhibited by protoporphyrin, which is a pigment of the egg shell, overlap partially with each other. Thus, problems inherent in the conventional optical egg inspecting method may be summarized as associated with establishment of technologies on (1) wavelength distribution and brightness of a source light, (2) qualitative classification of the egg shell colors, (3) systematic utilization of a diversity of spectral information. Also, with respect to the egg inspection as well as the egg packaging, (4) development of a method that can be used in the high speed multi-row transport system is desired.